Just because I newly started a game of "Ultima II" (yes, some people still do!) and encountered this now-infamous problem: The solution is the same - delete all content from the PLAYER-file. Just note that with GOG Galaxy the file in question is (also?) located in the cloud_saves-Folder. Took me a while to figure out that I had to delete the contents of that file as well. Now it seems to work perfectly.

If anyone is having this issue in 2021, you can go into the install folder and rename cloud_saves to cloud_saves_old. This is the location with the player file in it. Then restart the game and create a new char. On my pc the game is located here: C:\Program Files (x86)\GOG Galaxy\Games\Ultima 2